The use of a hand tool to tighten a band clamp has long been known. Band clamps are typically used to secure bundles of materials together and to secure pipes, wiring, etc. In one such application, a band clamp is applied to secure a protective metal braiding around a bundle of wiring which is connected to a plug or coupler known as a back shell.
Back shells are frequently used in military and aero-space applications where wiring carrying low voltage signals are conducted. Both the cables and the connectors must be protectively covered with a metallic substance to limit the harmful effects of radiation thereon. This metallic shielding must be without any "windows" (openings) and must in all parts have a ground connection with only low resistance to effectively minimize any electrical potential this "shielding" system may receive due to external or internal electromagnetic radiation (such as radio emission, cosmic rays, lightning strike, explosion of an atomic device, etc.). The diameter of the back shell body is typically larger than the diameter of the cable entering thereinto, and in order to have a satisfactory interconnection, a banding tool must be capable of applying a band clamp proximate the intersection of the back shell body and the cable entry stem. Thus the banding tool should be approximately the same width as the band clamp to be applied and should be capable of applying the band clamp from any direction.
One tool for tightening band clamps to a back shell is disclosed in U.S. Pat. No. 4,726,403, to Young et al., Feb. 23, 1988. The Young et al. device uses a toggle arrangement to tension the band clamp in place. Upon reaching the appropriate tension in the band clamp, the tool locks in a closed condition. To sever the tail from the tightened band clamp, a cutting arm must be rotated outwardly and upwardly from the side of the banding tool.
Due to the externally attached cutting device, the Young et al. banding tool is capable of applying a band clamp close to the back shell from only one direction. If a band is attempted to be connected from the opposite direction, the cutting device may prevent proper installation. The Young et al. tool is therefore limited in its application and becomes difficult to operate in confined spaces such as are found in aircraft fuselages.
Additionally, Young's tool uses toggles to transfer tension and toggles generally have a short power stroke in order to make the tool usable by an average person. Therefore, a larger size tool is required to sufficiently tension the band.
Another banding tool is disclosed in U.S. Pat. No. 4,928,738 to Marelin et al., May 29, 1990, assigned to the same assignee as the present invention. The '738 tool uses toggles to provide the power stroke and counteracting springs to achieve the desired tension in a band. It is necessary to force the band to bend around internal portions of the tool during tensioning. Additionally, the tool is not designed with overall width as a primary consideration.
Still another banding tool is disclosed in U.S. Pat. No. 2,087,655 to Prestwich, Jul. 20, 1937, the '655 device has a gripper section which holds one end of the band to be tensioned while a tensioning section grips and pull the other end of the band. The tensioning section comprises a double set of knurled wheels with a first set fixed and a second set movable. While the first set prevents slippage of the band, the second set tensions the band. While there is an angle between the tensioning section and the gripper section, this angular relationship does not provide the advantages of the present invention. Thus there is a need for a method and apparatus to allow tensioning of a band clamp to a back shell from either direction.